For a backlight used in a so-called liquid crystal television (TV), an LED chip which emits blue light as primary light, a red phosphor which is excited by the blue light and emits red light as secondary light, and a green phosphor which emits green light are used. The backlight emits white light which is obtained by mixing blue light, green light, and red light.
PTL 1 discloses a light emitting element which emits white light by exciting, using an LED for emitting blue light, divalent Eu-activated CaAlSiN3 (hereinafter, referred to as CASN phosphor) which is a nitride-based phosphor for emitting red light, and a green phosphor that emits green light.
In addition, an Eu-activated β-type SiAlON phosphor disclosed in, for example, PTL 2 has been appropriately used in the related art as a phosphor which emits green light.
In a case where an illumination device which emits white light by combining a blue LED, a red phosphor, and a green phosphor is used as a light source of a backlight of a liquid crystal television, there is a tendency for color reproducibility of the liquid crystal television to be improved by using a phosphor having a narrower peak wavelength of a light spectrum.
However, in a case where the CASN phosphor which is a phosphor disclosed in PTL 1 is used, a wavelength width of the light spectrum of the red phosphor is equal to or greater than 80 nm, and thus, the color reproducibility of red is not sufficient.
Accordingly, in order to realize a display device such as a liquid crystal television which can display deep red, development of a backlight which uses a Mn4+-activated K2SiF6 phosphor (hereinafter, referred to as KSF phosphor) disclosed in PTL 3 is in progress. A KSF phosphor has a spectrum of peak wavelength narrower than that of a CASN phosphor and can have further improved color reproducibility than the related art.